Method and apparatus for film drying of viscous compositions



B. COE

July 13, 1965 METHOD AND APPARATUS FOR FILM DRYING OF VISCOUSCOMPOSITIONS Filed Sept. 17. 1962 3 Sheets-Sheet 1 (Il...) NE

INVENTOR BERNARD cof:

BY ATT-YSY July 13, 1965 B. COE 3,194,297

METHOD AND APPARATUS FOR FILM DRYING OF VISCOUS COMPOSITIONS Filed Sept.17. 1962 Y 3 Sheets-Sheet 2 FIGB.

|NvENroR: BERNARD COE ATTYS.

B. COE

July 13, 1965 METHOD AND APPARATUS FOR FILM DRYING OF VISCOUSCOMPOSITIONS Filed Sept. 17, 1962 5 Sheets-Sheet 3 BERNARD COE ATTYS.

United States Patent O 3,194,297 f METHOD AND APPARATUS FOR FEM DRYING FWSCOUS COSITINS Bernard Coe, Cinnaminson Township, Burlington County,

NJ., assignor to Alco Chemical Corporation, Philadelphia, Pa., acorporation of Uhio Filed Sept. 17, 1962, Ser. No. 224,059 27 Claims.(Cl. 159-7) This invention relates to a method and apparatus for dryingviscous iiuid compositions containing a normally solid material, andmore particularly the invention relates to a novel method and apparatusfor drying such viscous fluid compositions quickly and effectively witha minimum application of high temperatures.

It is well known that thin layers of normally solid materials dispersedor dissolved in a volatile liquid will be dried more quickly by heatthan will thick layers of a similar composition. The reason for this isthat thin layers, in contrast to thick layers, provide a larger sur-facearea per unit volume and, therefore, allow a more rapid escape of thevolatile liquid as it passes from the liquid to the gaseous state by theapplication of heat. Therefore, it is not uncommon today for commercialdrying processes and` apparatus to employ some form of thin film orsmall droplet principle in drying various materials. i Generally a thinfilm is readily obtainable if the viscosity of the wet product allowsfluid ow. However, as the viscosity of the fiuid material increases, theow is correspondingly reduced and it is therefore necessary to exert anexternal force on the fiuid material to obtain a thin film, e.g.centrifugal force. ing a thin film such as scraping with a blade and thelike have also been used.

However, highly viscous compositions such as pastes, jellies, etc., donot readily lend themselves to the application of such external forces.A thin lm of these compositions can be obtained by dilution with variousvolatile liquid diluents. Adding such a volatile diluent to the viscouscomposition in the large volumes necessary to obtain the necessaryfluidity complicates the drying process by increasing the drying loadand handling requirements; resulting in more heat input per unit Weightof solid and an overall less commercially attractive process.

A further disadvantage in diluting viscous compositions is that suchdiluted compositions are frequently subjected to temperatures well inexcess of the boiling point of the volatile liquid portion thereof forsubstantial periods of time in order to achieve complete and efficientdrying. Many substances, particularly organic polymers, are adverselyaffected by exposure to high temperature for such prolonged periods oftime, and degradation of some polymers may take place.

A further difficulty encountered in thin film drying processes is thatupon drying the film frequently has the tendency to adhere or stick tothe drying surface and must be mechanically removed from the dryingsurface, for example by scraping or chipping. Various pretreatments ofthe drying surface, such as plating and the like, with certain metals,have been resorted to to minimize the sticking problem. However, thusfar such pretreatments, which are relatively expensive, have achievedonly limited success in the drying of many substances. Therefore, theremoval of a dried lm from a drying surface quickly and cleanly withoutresorting to extensive pretreatment of the drying surface and withoutresorting to extensive and unwieldy removal procedures has heretoforenot been successfully accomplished with many materials.

Another problem encountered in thin film drying has been the overheatingof the dried film caused in part by delay in removing the film from thedrying surface. That is, the heat remaining in the drying surface afterthe dry- Other means of obtainlgdg Patented July l, i965 ICC ingoperation has been completed often is sufficient to overheat andadversely aect the difficulty removable thin film which has been formedon the drying surface. This excessive heating -adversely aects thedesirable characteristics of the dried material, often rendering itrelatively useless for the purpose for which it is subsequentlyintended.

The handling of the dried thin film material upon removal from thedrying surface oftentimes heretofore has posed some difficulty. In thepast for example, with many materials it has been found that therelatively thin film formed upon drying broke, buckled and rolled orfolded over itself, thereby accumulating on the drying surface anddisrupting removal techniques. Moreover, subsequent to the removal ofthefilm from the supporting surface, it has often been necessary to subjectthe film to some mechanical sizing or breaking action whereby therequired size of the ydried particles is obtained.

Although methods other than film drying are known in the art, forexample, such methods as spray drying, pan drying and the like, thesemethods do not readily lend themselves to drying more viscouscompositions due to certain difficulties encountered in pumping,spreading, uniform heating, etc.

Various metals'and alloys are used inthe industry today as the dryingsurface. However, upon contact ofthe composition to be dried withcertain metal drying sur-faces, numerous unsatisfactory results areobtained. For example, with some materials it has been found thatcertain hot metals often act as catalysts under the heating conditionsof the drying process to produce undesirable chemical reactions with thematerials being dried. Further, the purity of the final dried product isoften unsatisfactory, eg., contamination resulting from metallicparticles lbeing leached from the metal drying surface is oftenencountered.

A principal object of the invention is to provide a novel method andapparatus for drying highly viscous fluid compositions containing anormally solid material whereby a thin film of the viscous compositionis obtained without resorting to conventional external forces ordilution, and the thus formed thin film is dried and readily removedfrom the drying surface while avoiding pretreatment of said dryingsurface.

Another object of the invention is to provide a novel drying method andapparatus whereby overheating of the film of dried material resulting indetrimental changes to certain desirable characteristics of the driedmaterial are avoided.

A further object of the invention is to provide a method for efficientlyforming thin films of highly Viscous fluid compositions in a rapid andefficient manner whereby the thickness of the film can be effectivelycontrolled.

Still another object of the present invention is to provide a method andapparatus for drying highly viscous compositions containing a normallysolid material by forming a thin film thereof on an expandable,resilient surface, and subsequently discharging the thin film from thesupporting surface in an eiiicient and rapid manner whereby aparticulate product of the desired particle size is obtained withoutresorting to complicated mechanical removing procedures or tosubsequenty mechanical particle sizing processes.

A still further object of the invention is to provide a novel processand apparatus whereby highly viscous compositions are efficiently driedin the form of a film and the dried solids are readily discharged fromthe film supporting surface in such a manner that degradation of thedried product by exposure to high temperatures for prolonged periods isavoided.

A particular object of the invention is to provide a novel method andapparatus for drying highly viscous compositions containing a normallysolid material wherein the, composition to -be Y ,dried is.contactedrwith a resilient, non-metallic drying surface; and a highdegree of purity of the dried product is maintained. V These and otherobjectsV of this invention and the various features and detailsof themethod thereof. and; of the` construction and'operation of .dryingapparatus thereof,

are more fullyY set forth hereinafter with vreference to the.-accompanying drawings wherein: Y

VFIGURE l is a plan -view of dryingapparatus illus- A:tratingV oneembodiment of Vthepresent invention;

FIGURE 2 is'a side elevational view,V partly in section,

i `of the apparatus set forth in FIGURE l; v

yFIGURE ,r3 is'a cross-sectional view takenalong the linev 3-3 of FIGUREl; Y

FIGURE 4 isa sectional, side elevation view taken Valong theline 4 4- ofFIGURE l;

FIGURE 5 is a cross-sectional View taken along the..

une s s ,of FIGURE 1;

Y FIGURE 6 is across-sectional view taken 'along the`V vline 6`6ofFIGURE l; .FIGURE .7 is a ,schematicv and elevational viewof aVsecond'embodiment ofthe invention;`

Cil

Afterthe lmhasbeen dried by removal Vof the Vvolat ile liquid, thesupport meanscanbe reduced insurface area ample by withdrawing allora'rportion of'thepressurized gas or liquid, or by reducing .themechanicalte'n sionV im-V VV posed 'on the' expandable .support means.Y

The :contraction forcesprodu'ced by reducing jthe expanding forcesfromth'e `supporting VmeanswareY sufficient. to overcomethefadhesivelforce between theydriedviscous iilrn and the. supportingmeans.'.,VrThereforejthei dry,

lm of normally solid Ymaterialis readily released from l V thesupporting means. If'thefnormallysolid,material*is FIGURES is anenlarged typical vertical section 1.

through the apparatus of FIGURE 7;

FIGURE/9 is an enlarged fragmentary, View of one of theelements'jillustrated in FIGURE 8;

embodiment .of the invention;

`. FIGURE 10 is a plan view, partly in section, ofa third FIGURE 1lY isa side .elevational view, partly in sec- 'f5 tion, taken along the linelle-1I of FIGURE 10, and- FIGURE l2 is an end elevational View takenalong the line 12-12 of FIGURE' 11. V

l Itis understood that the embodiments shown kand described hereinarefor illustrative purposes and mayY be4` changed orY modified .withoutdeparting from the spirtY and scope ofthe invention asfset forth intheyaccompanying claims.

It has beendiscoveredthat highly viscous iluid'compositions containinganormally solid material and a volatileV liquid may be formed into `thinfilms, thevolatile` Y liquid removed, and subsequently the resultingdried solids readily released from a drying surface, when said viscousfluid composition is applied as alayer toian expandable, resilientsupporting surface, the supporting sur- Y face is thereafter expanded inarea, the volatile liquid re- Ymovedyand'the supportingsurface isthencontracted. A

` thin ilm of the` viscous iuidcomposition is formed from the thickerfilm applied to the supporting surface by ap-l supporting means. Typicalexamples of expandable supporting means are an elastic endless 'beltwhich can be stretched vto increase; its surface area by applyinglateral l l yand/or longitudinalfextending forces, and Van elasticbladder or diaphragm which can be expanded in'surface` area'by inflationwith argas Vor liquid Y y By means ofy the inverntionfthe: viscous fluidVcomposi;

friable,rit will be releasedin the form of v.chips or flakes.'VOnthegother. handyifdt is somewhat flexiblepy it may be released intheformof aV sheet.'

. t The thickness and size .ofthe ,driedrfilmarel a function of thesurface' .area.-increase ,of the .exp'a'ndable'support-` ing means,thethicknessofthewet film'priorto exprimir-2` i siongof the supporting.means, anda@also=themannerin y vwhich the expandedxsupporung, meansisauowedio con: tract.

resultsV in the ,thin dried l'rnpbeing.released'fwithralmost toan'expandable, resilient; supporting 'surface` expandingsaid.supportingesurfaceto reduce jtheithicloaess of saidt. layer` ofviscousfluid'compositiomremoving volatile liquid. to render saidmaterial in a substantially dry condition,v and V separating .said:substantially dry" material.from said. v

. supporting surfacefby contracting said surface.;V Y The expandable,.resilient support meansf for, use V in this invention can vbemacle fromnumerous resilient; materials having they properties ofnatural;reclaimed,.vulcanized or.

tsynthetic rubber.- Itis preferred that the supportVrnateriaLV j be.expandcdl'to at' least. about 400% of its Voriginal-'surplyingextending .or stretching` forces to the expandablel Y face area and.preferablyfrom aboutgSOO to aboutLl00Q% Y of its originals'urface area.A typicalrubber. having'this Y Y Y property olexpandability, is;vulcanized `natural rubber Itis` particularlyV desirable y.thatthe-material 4whenzex-V panded,; be capable of recoveringrapidly toitsjoriginal.

i dimensions uponthe .release' of expandingy yforcesjapplied tion tobedried, in' the. form of Va layer, adheres toi they'v support means whichis inn a relatively relaxed condition ascompared to its expandedcondition, i.e. the Vexpandable support can beY ina completely. relaxedconditionat the time of applying the viscous composition thereto,or inbe expanded tok several and even many times its surface Y claims`meansany material regardless of-its` chemical come;` i position :thatpossessesmechanical .properties f similarV to V the specialproperties ofnatural. rubber, .thatfisphigh de'-,y a partly expandedstate. Theviscous Ymaterial may then V y thereto. As mentioned above, variousrubbers and elastomers, hereinaiter."called. rubben, suchlas;natural"andv l vsynthetic rubbersVand. plastic materialsicanbeVemployed. i

The term rubber` as employedjnfthe :specificationiand forrnabiiity.A andextendibility withfrapid recoveryrfrom V deformation, good mechanicalstrength andthe-like: Y

'i i Thus, a suitable.. rubber. may.` consist of natural rubber,

area at the time the visous'compositionis applied by' .V

large vdegreethe thickness of the lm after expansion` of the .supportwilldetermine the rate of drying,.thin filmsV drying more rapidlythanthiclc'iilms for any giyen mainfrared and hot gases lbeingpreferred.Moreoverpwhen applying vexpanding.forceslto the support means. Toa

inflatable type Vexpandable supporting means. are ern- V or a syntheticArubber. Synthetic rubbers produced byfY '(a) VPolymerizationV,butadienefalone ,orVvvitlrstyrenev (b) Interaction between sodiumpolysuldes andfdihalides (c) Poiyinerization of chlorfoprene j a' (d)Polyrnerization of'jisobutylene,and Y V l A Y (e) P,olymerizationV andplasticizatioriofvinyl chloridecan beus'ed. Y y

AOther Vrubber'or rubberr-lilcematerials' whichiare suitable for` use asthe expandable supporting means of this invention includeelastothiomersifPolyacrylates, polyesters,sili-` zcones and polymers inYwhich a variety' of ester, amideV and When theY expandable fsupportingv -me'ansl is V j stretched sufficiently to convert. the,`relativelyy thick layerof viscous `compositiontofa thin nlm,v the sizeofthe dried Y particles produced,i;iffthdried 'materialisfriablm c'anbe`Y V effectively'controlledby-thei rateVatfwhich the expanded. supportingfmeans "is V contracted. A' substantially` jins'tafn-Y Y' taneouscontractionof the supporting means, for example, V

urethane linkages occur. Suitable acrylic rubbers, silicone rubbers andpolyester rubbers may also be employed.

It is preferred that the expandable supporting means be comprised ofthose materials Which have a high favorable elasticity, i.e., thosematerials Which readily resume their original dimensions after removalof the force or forces which have produced an increase in dimensions,and which maintain their elastic integrity over an extended period ofuse. It is further preferred that those expandable materials which haverelatively high rates of recovery of original dimensions be employed. Atypical expandable material having these properties is vulcanizednatural rubber.

It is readily apparent from the foregoing that various compositionscontaining a normally solid material and a volatile liquid, whether inthe form of a solution, dispersion, paste, jelly or otherwise may bedried according to this invention. Of course, the use of the inventionis particularly advantageous in the drying of relatively viscouscompositions of the type which have been found to be difficult to forminto thin films according to prior known methods. In addition, thisinvention finds use in promoting chemical reactions wherein a solidproduct in dry form is desired. For example, Where the reaction producesa solid product and a liquid by-product, such as water, the inventioncan be used to dry the product and to drive the reaction to completionby removal of the liquid by-product. A typical reaction where theinvention may be used to advantage is inthe production of condensationproducts of alkylated aldehydes with phenols as described in U.S. PatentNo. 2,932,671. In the condensation reaction of this patent, liquidreactants are reacted to formthe solid condensate and by-product water.According to the method of this invention the water may be removed andthe condensate dried to obtain a substantially dry product in highyield. The expression fluid composition containing a normally solidmaterial as used in this specification andclaims is intended to includecompositions where the solid to be dried is formed during drying aswould be the case in carrying out the condensation reaction of theabove-mentioned patent utilizing the drying method of this invention. v

The normally solid material may be relatively brittle and friable whendried or may be relatively flexible. In the case of friable materials,this invention will ordinarily produce a particulate solid product.VWhere the dried material is relatively flexible, a sheet of material mayresult. In either case, 'the dried material should be readily separablefrom the expandable supporting surface upon contraction of thesupporting surface. Persons skilled in the art will not encounterv anydifficulty in selecting a proper supporting material for any particularsolid to be dried to avoid any significant adhesion between the driedmaterial and the expandable supporting means.

The composition to be dried is preferably applied as a layer to theelastic supporting means in the form of a solution, suspension,dispersion, slurry or the like. The composition to be dried should wetthe expandable, r'esilient supporting means so that upon expansion ofthe surfacearea of the supporting means, the composition wetting thesupporting means will also be extended, thereby being transformed into athin film. The viscosity of the composition should be sufficiently highso that the composition will not run. off of the supporting surface.Generally, the compositions to be dried should have a viscosity of atleast about 300 centipoises (Brookfield viscometer at rpm.) at 25 C. andpreferably at least about 1000 centipoises. As used in thisspecification and claims7 the expression viscous fluid composition meansa composition having physical properties, such as viscosity, surfacetension, the ability to wet the expandable supporting surface, etc., soas to be capable of being transformed into a thinner film on expansionof the supporting surface.

Solutions of water soluble resins such as polyacrylates, e.g. sodiumpolyacrylate and other alkaline metal salts of acrylic polymers andcopolymersvare readily adaptable to be dried by the herein describedmethod and apparatus for drying. Other compositions which may be driedinclude solutions and dispersions of polymeric materials such aspolyvinyl alcohol, various phenol formaldehyde condensation polymers,nitrogen containing polymers such as melamine formaldehyde condensationpolymers and urea condensation polymers. In addition, sugar and saltsolutions, and various natural gums and food products, either insolution or in suspension, can similarly be dried. Various suspensionsand slurries of materials such as zinc dimethyldithiocarbamate,dispersions of fine particles such as those found in paints and varioussuspensions of pharmaceutical materials can also be dried according tothe instant invention.

The advantages of this invention will be particularly apparent from thefollowing discussion of the use thereof in obtaining sodium polyacrylatein the form of a dry powder. Sodium polyacrylate may be produced by anemulsion polymerization process wherein acrylonitrile is polymerized inthe presence of a catalyst, and the resulting polymer is thereafterreacted with sodium hydroxide in the presence of water to produce thesodium salt of polyacrylic acid. This reaction composition comprisesgenerally about 10% polyacrylate total solids, and is extremely viscous,having a viscosity of from 60,000 to 300,000 centipoises (Brookfieldviscometer at 20 r.p.m.), at 25 C. Of course, handling sodiumpolyacrylate as a solid, dry product is much more attractivecommercially than handling a bulky, viscous solution comprising on theorder of water. Conventional drying methods are not readily adaptable todrying an aqueous sodium polyacrylate solution due to high viscosity ofthe solution and the difficulties encountered in pumping, spreading andthe like. Further, sodium polyacrylate adheres tenaciously to the dryingsurface upon evaporation of the liquid carrier and must be mechanicallyremoved therefrom by chipping or the like. However, when sodiumpolyacrylate is dried according to the teachings ofthe instantinvention, thin chips of the material are relatively easily producedefficiently, iu a high degree of purity at relatively low expense.

With reference to the drawings:

FGURES l to 6 illustrate apparatus according to one embodiment of thisinvention.

In FIGURE l, a viscous fluid composition 2l to be dried is applied as alayer by means of feed hopper 20 to endless expandable support means 22(see FIGURE 4). Support means 22 comprises an endless belt of rubberextending between rolls 24 and 26. Tenter clamps 28 engage the edges ofsupport means 22 by means of engaging devices 30 and 32, respectively,which are mounted on sprockets 34 :and 36 respectively. A series ofthese tenter clamps are mounted throughout drive chains 38 and 40 (seeFIGURE l). Drive sprockets 42 and 44 are driven by a motor 46, belt L28,and gear transmissions 50 and 5l, respectively. A series of idlersprockets 52 serve to guide drive chains 38 and 40 and the tenter clampsaffixed thereto between sprockets 34' and 42, and 36 and 44,respectively.

While tenter clamps 28 travel on guide chains 38 and l0 they are in alocked or closed position (see FIGURE 3) not only while engagingexpandable support means Z2 but also during their return fromdisengaging means `62 and 64 to engaging means 30 and 32 respectively.Therefore, prior to contacting engaging means 30 and 32 the tenterclaimps 23 are in a closed position as shown in FIGURE 3. Uponcontacting engaging means 30 and 32 the actuating arm 23a of tenterclamps 2S is actuated to an open position, i.e. the lower portion of theactuating arm 28a is pivoted inwardly toward the body of the tenterclamp 28 by contact of the upper portion of the actuating arm withengaging means 30 or 32, and thus is able to receive expandable supportmeans 22. Upon engaging the expandable support means at engaging means32 and 34, respectively, the tenter clamps 28 close, i.e. the lowerportion of each actuating arm 28a pivots outwardly away from the body ofthe tenter clamp and engages the expandable support means, and then thetenter clamps pass from aislado?? Y v 'the engaging area throughexpandingn Sdu/.here Y mechanical tension is applied'toV the edges `ofthe expand- 'able supporting means by a series of idler sprockets 52 onOpposite sides of the expandable supporting means which guidel thechains 38 and 40 to stretch the supporting means,

Vthereby extendingY the supporting means to approximately three timesits original width and also extending the sup`- porting meansklongitudinally thereby forming composition 21 into a thinlm asindicated by 21a (see FIGURE The expanded supported means with hlm 21aadhered thereto passes into heating `zone 56.

VHeating zone 56 is provided with infrared heating means 58 which serveto dry thin hlm 21a' by driving Vofi? any volatile liquid constituents`thereof, the vapors being;

'through contraction zone k59 wherein the expandedsupporting meansreturns to its original dimensions.

' VUponpassing through contraction'zone 59, thethus dried thin film isreleased from the elastic supporting Ymeans 22 in the form ofseparateparticles or flakes 21'!)` lth'eelastic support means 22 byreleasingmeans d?. and 64,

Vrespectively which contact actuating arm 28a and :open

' Y V portmeans 22 onto discharge'conveyor means 66.-

Y25 which are retained on the supporting means by guide rails 29 `and 31(see FIGURE l); Tenterfclamps 2S releaser 1t is noted that when thedried material 21a passes out Y f ,of drying zone-55, the adhesiveforces between the dried `material land the expandable supporting ymeans22v ,are

-overcome by the contraction forces produced Vin contrac- 'tion Vzone 59when'the expanding forces arereleased and Ythe expandable support meansis allowed to Vreturn to its original dimensions. Y Y

FIGURES 7 to 9V illustratera second'embodiment ofthe invention wherein-a plurality of expandable, resilienty surf faces of generallyvspheroidal configuration are-sequendried fand subsequently these.surfaces are expanded by pneumatic means to formathin film of thecompositionV `Vwhich is then dried. Upon contraction of the expandable'Y j surfaces, the dried material is released. f

More particularly, a rotary turret or supporting means wills rotatablymountedon a hollow shatt1tl2 anden-y closedin housing 104. Shaft 102.extends through the housing V104 and is supported onV either endthereof by journal blocks 106. YConnected to hollow shaft 162 areV gasintake and outletfmeans 168 and 110, respectively.r` As illustratedinFlGURE 9, hollow shaft 102 is divided longitudinally by a dividerplate 113 extending longitudi- V Vnally of the shaft 102 intotwo'chambers- 112 andrll,

which communicate withair` inletv andoutlet lines 1&8 and110,respectively. Turretltlll is provided `with interintermittentlythrough transmission 118. Transmission 118 also positive operates valvemeans containe'drinpneu-1v matic control unit126 which produces ahydraulic cycylic operation Vactuating hydraulic lift 128 when aspheroidal expandable surface is in vregistry with the'container means1291er the viscous composition. Therefore, in operation a deflatedspheroidalexpandable surfacey 136 is immersed in theviscous compositionto be dried when the hydraulic lift 128 is moved` from'the retractedVposition (seethev Referring more particularly nowfto 8,*,r`o-L taryturret 100. comprises hub portionfor a central" sec-` tion 132 with Vaseries Vofparms 134exteding`1adially'i therefrom. Arms 134'-V are fittedwi'th;inflatable, ex-,

pandable, Lspheroidal' surfaces or bladders jljfllfof Tubber;` Y Y YRotaryv turret 100 has acompartmentedcircular head 1136 The apparatusisdivid'edintoa series of;zones. .i There is an immersion zone138,"where` container' 129, secured :to piston 139.V of hydraulic1ift128 is located. v'Container Y.

compositionin immersion zone138 when:` container 129i]V is in the raisedposition.4 Subsequently ,container 129 is Vlowered `and, turretv 10()rotatedk clockwise with .af-f

coated bladder13tlj being introduced'into expansion zone 149 where itis'expandedrtoA the-requisite .size by being inatedwitha suitable gas,which maylbeahe'ated; V I l'pori 4continued irotation the ,inflatedAbladder passes; through ,7; e heating zone142 equippedwith banks ofinfra,.redrheat-z;V

ers 146. Y

The viscous compositioncoated Von eachdeljated bladi,

der 130 in immersion z'one138 'is subsequentlyy stretched..

to a thin lrn in expansion :zone 140e and dried in heating Y zone 142;;x Upon contraction oteachVbladderinfcontrac- Y A tion zone Y144;,1thethus dried thinflnrofymaterial 'isire-iV leasedfroin the `bladder and'falls in'particulate formfromy Y contractionzone V1514 ontoconveyor148f(see FIGURE f7);Y p' A moredetailed.lllustrationiof:theVina'tion fand-def ;iiation-meansY of thisembodirnent; 'offthe-iinvention is set forth in FIGUR-3.19.1` Turretf100, carryingsleeve bearping 1750,V which rotates with theturret,fisprovided-.with' forices151,1' and is mountedfor Arotatirmon stationary `shaft *102.Il Asdescribed earlier, shaft 1 0V2L.is partitionedV into a high pressureside 112 andalow pressure side1l4,v

Eachfarm-134has a hollowed.channelilSZfextending through vthe, lengthzthereof. v, Thishollowchannel'. cpm-'1l municates-withthe high`pressureside 112-1ofshaft 102y a by means ,ofA inlet-orice "154 inyshaft 102; iThereforeet during passagelthroughrthe V.expansion zone,air orr otherf p Y `gas is forced fromthehigh pressure sideqoflshaftlgthrough orifices,` ,151 ande into Ychannel 152 "of Pan arm V134 passingthrough head 158.

As each spheroidal expandable .surface Epassesrthrough' drying zone142', it kremainsi'n an ,expande/df staten-'by reasonof the presence or"the inflating gaswhich is'pre-f- Y' vented from escaping by the sea1formed` between sleeve u Vand shaft102. Wheneach vexpandable ,surface freaches-the contractionzone, the inflating gas-is permitted to escapethrough .,chaiinelr 152,; above Vol'ice 151,-` andY shaft 162 1 exhaustorifice: to low pressureV side 114i of and thenoutthrough gas outletmeans 116. f Y

Upon contraction of each expandable surface,;thedried v 'materiale isfseparated therefromg,and if friable fis-dis-n charged in the `ferm ofsolid particles.l Y 'f ment of the instant invention..V'llleecomposition:,tcrbel i dried is introduced'by rmeans of` tube.200]to ,feed-.hoppen 202 from which it'` sfapplied lasa laye'rnontoendlessYex pandable rubber support-.means k21M'. Endlesslexpandg f Y able:rubber supportmeansV 204 .isgcarriedbyV drive roll 228 and dvenrqll238iDrive roll ZZS'iand-.s'pr'ocltets f :206and 207 maybe driven;by.any,suitable meansfsuch as power transmission iunit `214 and sheaves-245Vvand 248V i y which, are interconnected by a suitable chain.: drivegenerally indicated` 211.2165 v The rolls, 228` and.238 int'urn Aarecarried on shafts 229YandV 239 respectively. Y To shafts. j

lull inthe intermittent rotation ofturret when a Y.

spheroidal surface is in registry with the container 129.j-

22.19 and 239 are also secured drive `sprockets 20.6 and 207Aand'drivenw'sproclets 212 andY l2131 respectively, YVwhitdl in' zoneV140, drying zone142 Vandv v 9 turn receive the cleat elements 222,andserve to propel the cleat elements longitudinally while maintainingthe side edges of the expandable support means 204 substantiallyparallel during its traverse through the apparatus. To this end suitableroller elements 234 secured to the chains 218 and 220 are engaged inguide rails or tracks 224 and 226. Cleat elements 222 are pivotallymounted on chains 218 and 220 with the outer edges of the chain 218having roller bearings 234 mounted thereon, which bear on guide means224 and 226.

Means is provided at 209 for expanding the central area of said supportmeans 204 in a vertical plane to eiiect a thinning of the viscous iluidcomposition prior to entering drying chamber 242 provided with infraredheating elements 236. The expanded support means is maintained in anexpanded state for the duration of the drying period. Expanding means209 comprises freely rotatable sheaves 208 and 210 supporting an endlessbelt thereon indicated at 230. Idler support rolls for said belt duringthe upper run thereof are indicated generally at 232. Suitable supportfor expanding means 209 is generally indicated at 244. As the extendiblesupport means passes from roller 228 to sheave 208 a significant`extension of the surface of the elastic support means 204 is achieved.Upon reaching 'expanding means 209,V expandable support means 204 isbrought to bear upon sheaves 208 and 210 and belt 230 and extendedthereby, Vidler rolls 232 providing additional supporty for theexpandable support means during this period of expansion `(see FIGURE11). Thus, the ilat expandable support means 204 is expanded into'atent-like structure as illustrated in FIGURE 12 while passing over thearea defined by sheaves 208 and 210. Thus, the expandable support means204 upon passing from roller 228 to sheave 208 is expanded laterally andlongitudinally thereby increasing the total surface area of the supportmeans and converts the layer `of viscous composition to a relativelythin film. Upon passing from drying chamber 242 where volatileV liquidis removed, the dried material is released from theexpandable supportingmeans 204 by contraction thereof in the form of discrete solid particleswhich pass onto discharge conveyor means 240.

Although in the various embodiments of this invention as shown in thedrawings and described in detail hereinabove the expandable supportingsurface is relatively smooth surfaced; a pocketed surface wherein thepockets serve as a plurality of small traps for the liquid compositionmay also be used, particularly with lower viscosity fluids.

The following example of the method of this invenion is given for thepurpose of illustration only and is not 'intended to limit the scope ofthis invention in any way.

A composition comprising sodium polyacrylate (less than 80% hydrolyzed)and 90% water having a viscosity of l80,000-2`00,000 centipoises(Brookield viscometer at r.p.m.) 'was applied to an inllatable rubberbladder to form a substantially continuous iilm about %6 thick. Thebladder was inllated and placed in a forced draft hot air ovenmaintained at `a temperature of 85 C. The inilated bladder was removedfrom the oven after l5 minutes andthe bladder was deated. The sodiumpolyacrylate separated from the bladder in the form of delicate dryflakes which were easily moved by a current of air. .Subsequent additionof the llakes to water showed they had not undergone any chemicalalteration duringv drying. v

Considerable modification is possible in the selection of the viscouslluid composition to be dried, the expandable supporting means employed,the method of removing volatile liquid from the Viscous fluidcomposition, the apparatus employed and the conditions under which theIdrying process is operated without departing from the scope of theinvention.

What is claimed is:

1. A method for drying a viscous lluid composition containing a normallysolid material which comprises applying a viscous lluid compositioncomprising said normally solid material and a volatile liquid to anexpandable, resilient supporting surface, expanding said supportingsurface to reduce the thickness of said layer of viscous fluidcomposition, removing volatile liquid to render said material in asubstantially dry condition, and separating said substantially drymaterial from said supporting surface by contracting said surface.

2. The method according to claim 1 in which said viscous iluidcomposition comprises a solution of said solid material in said volatileliquid.

3. The method according to claim 1 in which said viscous liuidcomposition comprises a dispersion of particles of said solid materialin said volatile liquid.

4. Thel method according to claim 1 in which said viscous lluidcomposition has a viscosity of at least 300 centipoises at 25 C.

5. The method according to claim 1 in which said viscous iluidcomposition is in the form of a paste.

6. The method according to claim 1 in which said viscous iluidcomposition comprises a solution of a synthetic organic polymer in avolatile organic solvent.

'7. The method according to claim 1 in which said viscous liuidcomposition comprises an aqueous dispersion of solid particles of asynthetic organic polymer.

8. The method according to claim 1 in which said volatile liquid isremoved by applying heat to said layer of said viscous composition.

9. Drying apparatus comprising an expandable, resilient surface forsupporting a layer of a viscous iiuid composition comprising a normallysolid material and a volatile liquid, means for depositing a layer ofsaid viscous luid composition on said expandable surface, means forincreasing the surface area of said expandable surface to .reduce thethickness of said layer of viscous fluid composition, means for removingsaid volatile liquid while said supporting surface is in an expandedcondition, and means for contracting said expandable surface.

10. Drying apparatus according to claim 9 in which said expandablesurface is substantially llat.

11. Drying apparatus according to claim 9 in which said means forremoving said volatile liquid comprises means for heating said layer ofviscous iiuid composition.

12. Drying apparatus according to claim 9 in which said expandablesurface comprises an elastomeric composition.

13. Drying apparatus according to claim 9 in which said expandablesurface is substantially spheroidal.

14. Drying apparatus according to claim 13 in which said means forexpanding and contracting said spheroidal surface comprises pneumaticmeans.

15. Drying apparatus comprising an endless belt of an expandable,resilient substance, means for advancing said Yendless belt, means forapplying a layer of a viscous liuid composition comprising a normallysolid material and a volatile liquid to the surface of said belt, meansfor increasing the transverse dimension of said endless belt afterapplication of said layer of said viscous liuid composition thereby todecrease the thickness of said layer, means for heating said layer ofviscous fluid composition while said belt is in an expanded condition,and means permitting said belt to contract to substantially its originaltranslverse dimension to release said solid material from said belt.

16. Drying apparatus according to claim 15 in which said belt comprisesrubber.

17. Drying apparatus comprising a plurality of substantially spheroidalsurfaces of expandable, resilient material 'spaced about the peripheryof rotatable supporting means for said spheroidal surfaces, containermeans for containing a viscous lluid composition comprising a normallysolid material and a volatile liquid into which said sphe- Vroidal'surfaces are Vimmersed `sequentially vto kacquit, "a

coating ofsaidV viscous fluid composition', pneumatic means forincreasing `the dimensions of each'spheroidal surface fffeafae? afterpassing through said container means and for sub-V j sequentlydecreasing the dimensions'V of said spheroidalsurfaces` prior tor'e-entering said container means `to remove the material therefrom, andheating means for heating and drying `said viscous liuid composition onsaid spheroidal surfaces While said spheroidal surfacesare of increaseddimensions.V v i V1.8. Drying apparatus according to claim 17in which`said Vspheroidal surfaces are formed of` rubber.

19,.` A-methodffor drying a viscous fluidcompositio containing anormally Vsolidtmaterial consisting .ofthe steps of supporting a belthaving `an expandable supportv surfacevfor movementalong a predeterminedpath, de-

' Y positing a viscous liuid composition comprising said normally solidmaterial and a volatile liquid on said support` surface at a supply zonealong said path, expanding said v support surface at least transverselyto the; direction of movementthereof at an, expansion zone downstream'of saidsupply zone thereby to reduce the thickness of said layer -ofviscous fluid composition, `removing volatilej Y V`liquid to render saidmaterial in a substantially dry condil tion in a drying zone downstreamof saidexpansion zone,

Yand permitting said belt to contract at a contraction Vzone`downstreamofgsaid drying Zone to'V separate said substantiallydrymaterial from saidsupport'surface. f

2?. A method for drying a viscous uid composition containing a vnormallysolid vmaterial consisting of the:

steps of supporting a belt-having an expandable support` Vsurfaceformovement along a predetermined path, depositing a viscous fluidcomposition comprising said normallysolid material and a volatileliquidon said support surface at a supply zone along said path, engaging oppo-Y site side edge portions of said belt during movementralong i,

said path, engaging v,said belt approximately centrally thereofdownstream of said supply Zone toform a terltlike structure and expandsaid support surfaceithereby* increasing at leastthe transversedimension of said -belt .and Vreducing the` thickness vof Vsaidlayer-ofviscous-fluidcomposition, removing volatile'liquidto render said matelrial in a substantially dry conditionV and thereafterY perv mittingcontraction of'said belt thereby `to separate *saidV f substantially drymaterial from saidl support surface'.`

` 21. A method Vfor drying a viscous uid cnmposition containing anormally solid `rmaterial consistingof the steps of applying a viscousliuid composition "comprising saidnormally solid material and a volatileliquid to*` the expandable peripheral support surface ofy an expandableballoon-like member, introducing a liuidvunder ,pressure into saidballoon-like member to expand said support surface thereof thereby toreduce the thicknessv of said layerv ofviscous fluid composition-appliedto the outer periph A eral surface thereof, removing the volatile liquidtoren'der the material in a substantially dry condition, andlreleasingthe fluid under pressure from the interior'of said balloon- Vlike memberto contract the outer peripheral surface thereof Vthereby to separatesaidy substantially dry Vmaterial fromsaid support surface. Y

22. AA method for drying a viscous fluid composition" containing anormally solid material consistingv `of the' steps -of moving in acircular path ,a plurality of balloon like members each having anexpandable outer peripheral y support surf-ace, applying a-viscousfluidcomposition com-j rialA in a substantially'dryfconditionyandreleasin`g ,jsaid n n fluid `under pressure from Vthe interiorof vsaidballoon-like v member `to contract the Souter periplrne'ralA `surface`thereof i thereby to separ-atesaid substantially `dry ,terial" fromsaid support surface.A

23. Inga dryingapparatm, atf-leastionefballoon-likeu member having'anexpandable Vexterior support jsurface,

means for applying a layer `of viscousQfluid `composition' t comprisinga normally solid 'materialV and a volatile liquid to the supportVsurface, offsaid'balloon-like member, means v for expandingtheouter'peripheralsurface of saidballo'omy v Ylike member-afteriapplication'jof said.V viscous liuidcornposition `theretotodecrease Vthefthick-uess fffsaidlayen means; fo'rheatingand dryingsaidfla'yefrv ofiyiscous fluid,`

composition while said balloon-like merr'ibery-isinV an expandedcondition, andmeans pe rrnittings'aidV balloon-like". member tocontractt release saidvisolidV-material Vfrom vsaid supportsurfaceV ,n YY Y 24; Drying apparatuscomprising ,a balloon-'like mem: ber having anexpandable ,outer{peripheralvsupport surface", means for actuatingsaideballoon-likefmeniber ina t continuous-path, a container along saidpath for al viscous .l 1 fluid composition comprising,a;-norma11ylSolidl'material and a volatileliquid, me-ansfo'reffecting [relativeactuajtion of said container;and }said'balloonlikemembefto Y' immersesaid balloon-like member into {said lviscous fluid composition toapply'said composition to lthe outerperipheral supportsurface of:saidiballoonalikeimernber, means for expanding the peripheral Vsurfaceof said: balloonalike rnemberpafter application'of said fluid.oompositionrthere to, heating means along' said pathforheatirig;anddrying` -saidfluid l compositionto'fornia substantiallysolid friable film of saidcompo'sition on said expanded supportsurface fduring movement along afportion lCif-said pathand .means along saidvpath for contracting ,saidysupport' surface after heating* of said fluidtherebyto rupture said substantially; f dry jiilm vandtofremove saidsubstantiallydried material t, member when aY balloon-like member,aridqsaid-container are in Vregistryto immerse; saidballoon-like;.memberintof said viscous fluid compositionitoapply'Qa.layer'of said"v composition to the outer peripheral ,supportsurfaceloi, said balloon-likeInlrvrlbfaf,A meansrfor, ,expahdi'ngy thecperipheralsurface of saidballoon-likemember in anexpari-L Y, `sionzoneafterV applicationiofya layer offsaid huid corn-` 'f prising saidnormally solid material and a volatile liquid tothe expandableperipheral support surface -of each balloon-like member at a supplyzonealong said path,

introducing a fluid under'pressure into said balloon-like member at anexpansion zone along said path to expandV form of flakes.

position` thereto, "heating meansl alongV said path for heating and,dryingV said ,fluid composition to form ai substantially Ysolid friablefilm of said `compositionv on;said.expanded support' surfaceduringmovement alongfa portion of said path and meansk along said: path forcontractingysaidfs'u'p-V port surface in aontrac'tifon; zoneeafterheating rof said, fluid thereby to rupture saidsubstantially'drylilrn andto:

remove said substantially dried materiaktherefrominthe 262 Dryingapparatusr'as claimedy iniclaini'ZS; including a rotatablymounted'turrethaving a hubportion and a` plurality of hollow armsVextending"radially from :said hub portiongeach of said .arms mountinigaballoon-like `mem-- ber at tits freev end l.; y Y ,Y

Z7". Drying apparatus asclaimedin laimrZi` including astationaryhollowshaftfonV jwhichaidturret rotates,`

said support surface vthereby toreduce the thickness of lsaid layer ofviscous liuid composition appliedto` the outer Vperipheralsurfacerthereof, removing the' volatile,

4liquid at a drying zone along said path to render `the matesaid shaftdivided longitudinally;` intogan vinlet chamberi' and an outlet chamberand ,having radially extending inlet and outlet orifices communicating,respectively with-said inlet' and outletchambers andY means forsupplying a Huidv under pressure to said'inlet chamber, whereby uponrotar;

.tion of said turret relative Vto'said shaft, feachofsaid arms`registermg With-said inlet orilicev in 'said exnansionzoue to permitsaid pressure uid to expand said member and registering with said outletorifice to exhaust said pressure uid to permit contraction of saidmember in said contrac- :tion zone.

References Cited by the Examiner UNITED STATES PATENTS 600,676 3/98Menzis 118-34 2,360,257 10/44 Muller et al. 34-39 X 14 Young. Ryden.Pfefer 198-34 Pfeiffer. Ames. Horn.

NORMAN Y'UDKGFF, Primary Examiner.

GEORGE D. MITCHELL, Examiner.

1. A METHOD FOR DRYING A VISCOUS FLUID COMPOSITION CONTAINING A NORMALLYSOLID MATERIAL WHICH COMPRISES APPLYING A VISCOUS FLUID COMPOSITIONCOMPRISING SAID NORMALLY SOLID MATERIAL AND A VOLATILE LIQUID TO ANEXPANDABLE, RESILIENT SUPPORTING SURFACE, EXPANDING SAID SUPPORTINGSURFACE TO REDUCE THE THICKNESS OF SAID LAYER OF VISCOUS FLUIDCOMPOSITION, REMOVING VOLATILE LIQUID TO RENDER SAID MATERIAL IN ASUBSTANTIALLY DRY CONDITION, AND SEPARATING SAID SUBSTANTIALLY DRYMATERIAL FROM SAID SUPPORTING SURFACE BY CONTRACTING SAID SURFACE.